In the making and use of fiber optic system components from specialty fibers it is known that the components customarily have response characteristics dependent on the temperature at which the components are used. To obtain fixed responses despite varying environmental temperatures various complex and expensive solutions have been proposed in the past, such as housing the components in temperature controlled containers or adding temperature sensitive mechanical stressing features to the fiber. Other attempts at solving the problem have been directed to the selection and proportioning of the constituents of the core and cladding materials of fibers, used in making the components, whereby components made from the fibers inherently have good temperature insensitivity and can hopefully be used in many applications without the need for temperature controlled containers, stressing mechanisms or the like.
Prior efforts toward providing an optical fiber with high temperature insensitivity by core and cladding constituent control are revealed by U.S. Pat. Nos. 5,703,978, 5,949,934 and 6,201,918. These patents suggest that changes with respect to temperature of a long-period grating made from a given fiber are directly related to changes in the fiber's effective refractive index neff with respect to temperature. These patents still farther suggest that a fiber with high temperature insensitivity can be made by formulating the constituents of the core and cladding materials such that the characteristic curve of the core index vs. temperature and the characteristic curve of the cladding index with respect to temperature have substantially the same shape (see FIG. 5 of the '978 patent) so that at every reasonable temperature the rate of change of the core index,             ⅆ              n        core                    ⅆ      T        ,is equal to the rate of change of the cladding index,             ⅆ              n        clad                    ⅆ      T        ,to accordingly make the rate of change of the fiber effective index acceptably low or zero at all temperatures.
In regard to the disclosures of the foregoing patents, Inventors have found that it is impractical, and perhaps impossible, to in all cases formulate core and cladding materials such that a grating or other device made with the fiber has the requisite temperature performance. Accordingly, it is an object of the present invention to address one or more of the foregoing disadvantages or deficiencies of the prior art.